Non linear equation of state and effective phantom divide in brane models

TL;DR

This paper compares brane gravity models, specifically DGP and RS-II, using a non-linear equation of state, revealing how brane tension influences energy conditions and cosmic acceleration.

Contribution

It introduces a non-linear equation of state to analyze brane models, highlighting the impact of brane tension on energy conditions and universe acceleration.

Findings

In DGP model, SEC is always violated, leading to acceleration.

In RS-II model, SEC is not violated for certain density ranges, resulting in deceleration.

Brane tension significantly affects the behavior of phantom energy and cosmic dynamics.

Abstract

Here, DGP model of brane-gravity is analyzed and compared with the standard general relativity and Randall-Sundrum cases using non-linear equation of state. Phantom fluid is known to violate the weak energy condition. In this paper, it is found that this characteristic of phantom energy is affected drastically by the negative brane-tension $\lambda$ of the RS-II model. It is found that in DGP model strong energy condition(SEC) is always violated and the universe accelerates only where as in RS-II model even SEC is not violated for $1 < \rho/\lambda < 2$ and the universe decelerates.